置氢0.12%H对Ti-0.3Mo-0.8Ni氩弧焊接接头组织演变影响

Effect of 0.12wt.% hydrogen addition on microstructural evolution of Ti-0.3Mo-0.8Ni alloy argon-arc welded joints

摘要:

基于光学显微镜、X射线衍射仪和透射电子显微镜分析，研究了0.12 wt.% H 对Ti-0.3Mo-0.8Ni氩弧焊接接头微观组织演变影响，揭示了氢元素对无损焊接接头组织特性影响规律。研究结果表明：氢化物析出促使焊接接头初始组织发生变化，置氢量增加有助于焊接接头微观组织中β相析出。薄片状的面心立方δ氢化物均匀分布在置氢量为0.12 wt.% H的焊接接头中，且仅能从层片状α相中析出，但无法从转变β相中析出。δ氢化物的析出与αH相分解反应：αH→α (贫氢区) + δ (富氢区)相关，富氢区最终转变为δ氢化物. 置氢焊接接头组织中的位错分布不均匀，δ氢化物析出产生的应力场引起的晶格畸变直接导致了析出δ氢化物附近有相对密度高的位错分布。

Abstract:

The effects of hydrogen addition (0.12 wt.% H) on microstructural evolution in Ti-0.3Mo-0.8Ni alloy argon-arc welded joints have been investigated using optical microscope (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) to reveal the influence of hydrogen on the characteristics of defect-free titanium alloy welded joints. The results show that hydride precipitation changed the initial microstructure of the welded joints, the increase of hydrogen content was more favorable for the beta phase precipitation. Face centered cubic δ hydride evenly distributed in the hydrogenated 0.12 wt.% H welded joints, the lamellar δ hydride could only precipitate from the lamellae alpha, and not from the transformed beta phase. Formation of δ hydride was associated with the result of αH phase separation reaction: αH→α (H lean region) + δ (H rich region), and H rich regions finally transformed to the δ phase. The dislocation distribution was heterogeneous and there was a relatively high density of dislocations in the vicinity of the precipitated δ hydride, which were caused by the lattice distortion due to the stress field generated by the hydride precipitation.